JP2545170B2 - Wafer sticking adhesive sheet and wafer dicing method - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive sheet for wafer sticking and a wafer dicing method, and more specifically,
TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive sheet for wafer sticking and a wafer dicing method, which can reduce dicing dust generated when a semiconductor wafer is cut and separated into small pieces.

[0002]

BACKGROUND OF THE INVENTION Semiconductor wafers of silicon, gallium arsenide and the like are manufactured in a large diameter state, and this wafer is cut and separated (diced) into element pieces and then transferred to the next step, a mounting step. . At this time, the semiconductor wafer is subjected to the steps of dicing, cleaning, drying, expanding, picking up, and mounting while being adhered to the adhesive sheet in advance.

In the processes from the dicing process of semiconductor wafers to the picking-up process, an adhesive sheet in which an adhesive is applied on a base material has been used. In such an adhesive sheet, a polyolefin film, a polyvinyl chloride film, or the like is used as a base material.

At the time of wafer dicing, the pressure-sensitive adhesive layer or a part of the base material film may be cut together with the wafer, and dicing dust may be generated from the pressure-sensitive adhesive sheet to contaminate the wafer. The dicing debris generated when the polyolefin-based substrate film is scraped off by the dicing blade has a thread-like shape, and an adhesive agent is attached to the thread-like debris. If such thread-like waste adheres to the diced chips, it cannot be easily removed, and the yield rate of the chips decreases.

[0005]

DISCLOSURE OF THE INVENTION The present invention is intended to solve the problems associated with the prior art as described above, and in particular, when a polyolefin film is used as a base film, dicing scraps which are easily generated from an adhesive sheet. The purpose is to reduce.

[0006]

SUMMARY OF THE INVENTION A wafer-adhesive pressure-sensitive adhesive sheet according to the present invention comprises a substrate and an adhesive layer, and the substrate film is an ethylene-methylmethacrylate copolymer film.

In the wafer dicing method according to the present invention, when a wafer is attached to a wafer-attaching adhesive sheet consisting of a base material and an adhesive layer and the wafer is diced, ethylene / methyl methacrylate is used as the base material film. The use of the copolymer film is characterized in that the amount of dicing chips generated during wafer dicing is reduced.

[0008]

DETAILED DESCRIPTION OF THE INVENTION As a pressure-sensitive adhesive sheet for wafer adhesion according to the present invention, a pressure-sensitive adhesive layer 2 is formed on an ethylene / methyl methacrylate copolymer film (base film) 1 as shown in FIG. 1, for example. Adhesive sheet 10
Can be illustrated. In order to protect the pressure-sensitive adhesive layer 2 before using the pressure-sensitive adhesive sheet 10, it is preferable to temporarily adhere the peelable sheet 3 to the upper surface of the pressure-sensitive adhesive layer 2 as shown in FIG. Further, as shown in FIG. 3, a reinforcing layer 5 may be provided on the surface of the base material opposite to the pressure-sensitive adhesive layer 2. The reinforcing layer 5 can be laminated on the base film 1 via the adhesive layer 4. By providing such a reinforcing layer 5,
Problems such as tape tearing during expansion can be prevented. As the reinforcing layer 5, a film having excellent elasticity such as a polyolefin film or a vinyl chloride film is used without particular limitation.

The pressure-sensitive adhesive sheet 10 according to the present invention may have any shape such as a tape shape or a label shape. As the base film 1, an ethylene / methylmethacrylate copolymer film obtained by copolymerizing ethylene and methylmethacrylic acid is used. In this ethylene / methyl methacrylate copolymer film, the constitutional unit derived from ethylene is preferably 50 to 99% by weight,
Particularly preferably 80 to 95% by weight, and further preferably 9
It is present in an amount of 0-95% by weight. The structural unit derived from methylmethacrylic acid is preferably 50 to 1
%, Particularly preferably 20 to 5% by weight, more preferably 10 to 5% by weight.

The substrate film 1 may be composed of one resin film as described above, or may be a laminate of two or more films. The thickness of such a base film 1 is usually 40 to 200 μm, preferably 60 to 150 μm.

Such an ethylene / methyl methacrylate copolymer film is excellent in mechanical properties such as elasticity and strength. When such a film is used as a base film of a pressure-sensitive adhesive sheet for wafer sticking, it is possible to reduce the generation of thread-like dicing chips during wafer dicing,
In addition, the pressure-sensitive adhesive sheet can be expanded without any trouble.

In the present invention, the pressure-sensitive adhesive layer 2 is formed on the substrate film 1 as described above and used for dicing a wafer. As the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 2, conventionally known ones can be widely used, but an acrylic pressure-sensitive adhesive is preferable, and specifically, a homopolymer having an acrylic ester as a main constituent monomer unit. Further, an acrylic polymer selected from copolymers, copolymers with other functional monomers, and mixtures of these polymers are used. For example, as the acrylate ester, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, glycidyl methacrylate, 2-hydroxyethyl methacrylate, and the like, and those in which the above methacrylic acid is replaced with acrylic acid, for example, are also preferable. Can be used.

Further, in order to enhance the compatibility with the oligomer described later, monomers such as acrylic acid or methacrylic acid, acrylonitrile and vinyl acetate may be copolymerized. The molecular weight of the acrylic polymer obtained by polymerizing these monomers is 1.0 × 10 ^{5 to} 10.0 × 10 ⁵ , preferably 4.0 × 10 ^{5 to} 8.0 × 10 ⁵ . is there.

Further, by including a radiation-polymerizable compound in the pressure-sensitive adhesive layer as described above, the adhesive force can be lowered by irradiating the pressure-sensitive adhesive layer with radiation after the wafer is cut and separated. . Examples of such radiation-polymerizable compounds include those disclosed in JP-A-60-196,95.
No. 6, and JP-A-60-223,139, a low molecular weight compound having at least two photopolymerizable carbon-carbon double bonds in a molecule capable of being three-dimensionally reticulated by light irradiation. Is widely used. Specifically, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hexaacrylate or 1,4- Butylene glycol diacrylate, 1,6-hexanediol diacrylate,
Polyethylene glycol diacrylate, commercially available oligoester acrylate, etc. are used.

Further, as the radiation-polymerizable compound, a urethane acrylate-based oligomer may be used in addition to the above-mentioned acrylate-based compound. The urethane acrylate-based oligomer is a polyol compound such as polyester type or polyether type, and a polyvalent isocyanate compound such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4. -Acrylate or methacrylate having a hydroxyl group, for example, a terminal isocyanate urethane prepolymer obtained by reacting xylylene diisocyanate, diphenylmethane 4,4-diisocyanate, etc., such as 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate , 2-hydroxypropyl methacrylate, polyethylene glycol acrylate, polyethylene glycol methacrylate, etc. Obtained by. This urethane acrylate-based oligomer is a radiation-polymerizable compound having at least one carbon-carbon double bond.

As such a urethane acrylate-based oligomer, the molecular weight is particularly 3,000 to 30,000, preferably 3,000 to 10,000, and more preferably 400.
It is preferable to use one having a thickness of 0 to 8000 because even if the surface of the semiconductor wafer is rough, the adhesive does not adhere to the chip surface when the wafer chip is picked up. When a urethane acrylate oligomer is used as a radiation-polymerizable compound, it is disclosed in JP-A-60-196,95.
Compared with the case of using a low molecular weight compound having at least two photopolymerizable carbon-carbon double bonds in the molecule as disclosed in Japanese Patent Publication No. 6, a very excellent adhesive sheet can be obtained. That is, the adhesive strength of the pressure-sensitive adhesive sheet before irradiation with radiation is sufficiently large, and the adhesive strength is not sufficiently reduced after irradiation with radiation, so that the adhesive does not remain on the chip surface at the time of picking up the wafer chip.

Regarding the compounding ratio of the acrylic pressure-sensitive adhesive and the urethane acrylate oligomer in the pressure-sensitive adhesive, the urethane acrylate oligomer may be used in an amount of 50 to 900 parts by weight based on 100 parts by weight of the acrylic pressure-sensitive adhesive. preferable. In this case, the adhesive sheet obtained has a large initial adhesive force, and the adhesive force is greatly reduced after irradiation with radiation, and the wafer chip can be easily picked up from the adhesive sheet.

If desired, the pressure-sensitive adhesive layer 2 may contain, in addition to the above-mentioned pressure-sensitive adhesive and the radiation-polymerizable compound, a compound which is colored by irradiation with radiation. By including a compound to be colored in the pressure-sensitive adhesive 3 by such radiation irradiation, after the pressure-sensitive adhesive sheet is irradiated with radiation, the sheet is colored, and thus the detection accuracy when detecting a wafer chip by an optical sensor is improved. As a result, malfunction does not occur when picking up a wafer chip. Further, it is possible to obtain an effect that it is possible to immediately visually confirm whether or not the adhesive sheet is irradiated with radiation.

The compound that is colored by irradiation with radiation is a compound that is colorless or light-colored before irradiation with radiation, but is colored by irradiation with radiation, and a preferable specific example of this compound is a leuco dye. As the leuco dye, conventional triphenylmethane type, fluorane type, phenothiazine type, auramine type and spiropyran type dyes are preferably used. Specifically, 3- [N-
(P-Tolylamino)]-7-anilinofluorane, 3
-[N- (p-tolyl) -N-methylamino] -7-anilinofluorane, 3- [N- (p-tolyl) -N-ethylamino] -7-anilinofluorane, 3-diethylamino -6-Methyl-7-anilinofluorane, crystal violet lactone, 4,4 ', 4 "-trisdimethylaminotriphenylmethanol, 4,4', 4"
-Trisdimethylaminotriphenylmethane and the like.

Examples of the color developer that is preferably used with these leuco dyes include conventionally used phenol formalin resin prepolymers, aromatic carboxylic acid derivatives, and electron acceptors such as activated clay. When changing the value, various known color formers can be used in combination.

Such a compound which is colored by irradiation with radiation may be dissolved in an organic solvent or the like and then contained in the adhesive layer, or may be made into a fine powder and contained in the adhesive layer. . This compound is added to the adhesive layer in an amount of 0.01 to
It is desirable to use in an amount of 10% by weight, preferably 0.5-5% by weight. If the compound is used in an amount exceeding 10% by weight, the radiation applied to the pressure-sensitive adhesive sheet may be excessively absorbed by the compound, so that the curing of the pressure-sensitive adhesive layer may be insufficient. Is 0.01% by weight
If it is used in an amount less than the above range, the adhesive sheet may not be sufficiently colored upon irradiation with radiation, and malfunction may easily occur during pickup of the wafer chip.

In some cases, the pressure-sensitive adhesive layer 2 may contain a light-scattering inorganic compound powder in addition to the above-mentioned pressure-sensitive adhesive and the radiation-polymerizable compound. By including such a light-scattering inorganic compound powder in the pressure-sensitive adhesive layer 2, even if the surface of an adherend such as a semiconductor wafer becomes gray or black for some reason, the pressure-sensitive adhesive sheet is irradiated with radiation such as ultraviolet rays. Then, even in the grayed or blackened part, the adhesive strength is sufficiently reduced,
Therefore, it is possible to obtain an effect that the adhesive does not adhere to the surface of the wafer chip when the wafer chip is picked up, and has sufficient adhesive force before irradiation of radiation.

This light-scattering inorganic compound is
V) or an electron beam (EB) or the like, which is a compound capable of diffusely reflecting this radiation, and specifically, silica powder, alumina powder, silica-alumina powder, mica powder Are exemplified. The light-scattering inorganic compound is preferably a compound that reflects the above-mentioned radiation almost completely, but of course, a compound that absorbs the radiation to some extent can also be used.

The light-scattering inorganic compound is preferably in the form of powder and has a particle size of 1 to 100 μm, preferably 1 to 2
It is preferably about 0 μm. The light-scattering inorganic compound is contained in the pressure-sensitive adhesive layer in an amount of 0.1 to 10% by weight, preferably 1% by weight.
It is preferably used in an amount of ˜4% by weight. When the compound is used in the pressure-sensitive adhesive layer in an amount of more than 10% by weight, the adhesive force of the pressure-sensitive adhesive layer may be decreased.
When the content is less than wt%, when the semiconductor wafer surface is grayed or blackened, even if the portion is irradiated with radiation, the adhesive force may not be sufficiently reduced and the adhesive may remain on the wafer surface during pickup.

The pressure-sensitive adhesive sheet obtained by adding the light-scattering inorganic compound powder to the pressure-sensitive adhesive layer can be used even when the semiconductor wafer surface is grayed or blackened for some reason. It is considered that the reason why the adhesive strength of this part, when it is irradiated with radiation, is sufficiently reduced in this part is as follows. That is, the pressure-sensitive adhesive sheet 10 used in the present invention has the pressure-sensitive adhesive layer 2, but when the pressure-sensitive adhesive layer 2 is irradiated with radiation, the radiation-polymerizable compound contained in the pressure-sensitive adhesive layer 2 cures and its The adhesive strength will be reduced.
However, a grayed or blackened portion may occur on the semiconductor wafer surface for some reason. When the adhesive layer 2 is irradiated with radiation in such a case, the radiation passes through the adhesive layer 2 and reaches the wafer surface. However, if there is a grayed or blackened portion on the wafer surface, the radiation will be emitted at this portion. It is absorbed and no longer reflects. Therefore, the radiation that should originally be used for curing the pressure-sensitive adhesive layer 2 is absorbed in the grayed or blackened portion, and the pressure-sensitive adhesive layer 2 is insufficiently cured, and the adhesive strength is not sufficiently reduced. become. Therefore, it is considered that the adhesive may adhere to the chip surface when the wafer chip is picked up.

However, when the light-scattering inorganic compound powder is added to the pressure-sensitive adhesive layer 2, the irradiated radiation collides with the compound and changes its direction before reaching the wafer surface. For this reason, even if there is a grayed or blackened portion on the wafer chip surface, the diffusely reflected radiation sufficiently enters the area above this portion, and thus the grayed or blackened portion is also sufficiently cured. To do. For this reason,
By adding the light-scattering inorganic compound powder to the adhesive layer, even if there is a grayed or blackened portion on the surface of the semiconductor wafer for some reason, curing of the adhesive layer becomes insufficient at this portion. Therefore, the adhesive does not adhere to the chip surface when the wafer chip is picked up.

Further, in the present invention, abrasive grains may be dispersed in the base film. This abrasive grain has a grain size of 0.5-
The thickness is 100 μm, preferably 1 to 50 μm, and the Mohs hardness is 6 to 10, preferably 7 to 10. In particular,
Green carborundum, artificial corundum, optical emery, white alundum, boron carbide, chromium (III) oxide, cerium oxide, diamond powder and the like are used. Such abrasive grains are preferably colorless or white. Such abrasive grains are contained in the base film 2 in an amount of 0.5 to 70% by weight, preferably 5 to 50% by weight.
Present in an amount of. Such abrasive grains are particularly preferably used when the cutting blade is used at a depth that cuts not only the wafer but also the base film 2.

By including the above-mentioned abrasive grains in the substrate film, even if the cutting blade cuts into the substrate film and the adhesive adheres to the cutting blade, the abrasive effect of the abrasive grains causes The clogging can be easily removed.

The initial adhesive force can be set to an arbitrary value by mixing an isocyanate type curing agent in the above-mentioned pressure-sensitive adhesive. As such a curing agent,
Specifically, a polyvalent isocyanate compound such as 2,4
-Tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate,
1,4-xylene diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-
2,4'-diisocyanate, 3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, lysine isocyanate and the like are used.

Further, in the case of UV irradiation in the above-mentioned pressure-sensitive adhesive, by mixing a UV initiator, the polymerization and curing time by UV irradiation and the UV irradiation amount can be shortened.

Specific examples of such a UV initiator include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether,
Examples thereof include benzyl diphenyl sulfide, tetramethyl thiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl and β-chloranthraquinone.

The procedure of the wafer dicing method according to the present invention will be described below. When the peelable sheet 3 is provided on the upper surface of the adhesive sheet 10, the sheet 3 is removed,
Next, the pressure-sensitive adhesive layer 2 of the pressure-sensitive adhesive sheet 10 is placed face up, and as shown in FIG. 3, the semiconductor wafer A to be processed by dicing is attached to the upper surface of the pressure-sensitive adhesive layer 2. In this attached state, the wafer A is subjected to various processes such as dicing, cleaning and drying. At this time, since the wafer chip is sufficiently adhered and held on the adhesive sheet by the adhesive layer 2, the wafer chip does not fall off during the above steps.

Next, each wafer chip is picked up from the adhesive sheet and mounted on a predetermined base.
At this time, prior to or at the time of pickup, as shown in FIG. 5, the adhesive layer 2 of the adhesive sheet 10 is irradiated with ionizing radiation B such as ultraviolet rays (UV) or electron beams (EB) to obtain an adhesive layer. The radiation-polymerizable compound contained in 2 is polymerized and cured. Thus, when the pressure-sensitive adhesive layer 2 is irradiated with radiation to polymerize and cure the radiation-polymerizable compound, the adhesive force of the pressure-sensitive adhesive is greatly reduced, and only a slight adhesive force remains.

The radiation of the pressure-sensitive adhesive sheet 10 is preferably performed from the surface of the base film 1 on which the pressure-sensitive adhesive layer 2 is not provided. Therefore, as described above, when UV is used as the radiation, the base film 1 needs to be light transmissive, but when EB is used as the radiation, the base film 1 is not necessarily light transmissive. No need.

As described above, the adhesive layer 2 in the portion where the wafer chips A ₁ , A _2, ... Are provided is irradiated with radiation to reduce the adhesive force of the adhesive layer 2, and then the adhesive sheet 10 is attached. Transfer to a pick-up station (not shown), and
As shown in FIG. 1, the tip A ₁ ... to be picked up is pushed up by the push-up needle bar 6 from the lower surface of the substrate film 1 according to a conventional method, and this tip A ₁ ... is picked up by, for example, a suction collet 7, Mount on the designated base. In this way, the wafer chip A
_When picking up ₁ , A ₂ ..., the adhesive can be easily picked up without adhering to the wafer chip surface, and a chip of good quality without contamination can be obtained. Radiation irradiation can also be performed at the pickup station.

Irradiation does not necessarily have to be performed once at once over the entire sticking surface of the wafer A, and may be partially divided into several times. For example,
For each of the wafer chips A ₁ , A _2, ... to be picked up, irradiation is performed by a radiation irradiation tube that irradiates only the corresponding back surface to reduce the adhesive strength of only the adhesive at that portion, and then the push-up needle Wafer chips A ₁ , A ₂ ...
You can also push up and pick up sequentially.
FIG. 7 shows a modified example of the above-mentioned radiation irradiation method. In this case, the inside of the push-up needle bar 6 is hollow, and a radiation source 8 is provided in the hollow portion to simultaneously perform radiation irradiation and pickup. In this way, the apparatus can be simplified and the pick-up operation time can be shortened at the same time.

[0037]

As described above, according to the present invention, it is possible to prevent the generation of dicing scraps, and also to maintain the elasticity and strength of the polyolefin film, so that the expanding can be easily performed. be able to.

[0038]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0039]

EXAMPLES 100 parts by weight of acrylic pressure-sensitive adhesive (copolymer of n-butyl acrylate and acrylic acid) and molecular weight of 80
100 parts by weight of urethane acrylate-based oligomer of 00, 10 parts by weight of curing agent (diisocyanate-based), and UV
A pressure-sensitive adhesive composition was prepared by mixing 5 parts by weight of a curing reaction initiator (benzophenone-based).

An ethylene / methylmethacrylate copolymer film [ethylene: methylmethacrylic acid = 90: 10 (weight ratio)] (thickness: 100
(μm) to have a thickness of 10 μm to prepare an adhesive sheet.

A 5-inch silicon wafer was attached on the adhesive layer of the obtained adhesive sheet, and the wafer was diced. Dicing was performed under the following two conditions. Dicing condition 1 Dicer: 2H / 6T manufactured by DISCO Blade rotation speed: 30,000 r. p. m. Dicing speed: 100 mm / sec Dicing depth: 30 μm from tape surface Blade thickness: 25 μm Dicing size: 5 mm × 5 mm Cut mode: Down cut Dicing condition 2 Dicer: DISCO 2H / 6T Blade rotation speed: 40,000 r. p. m. Dicing speed: 100 mm / sec Dicing depth: 30 μm from tape surface Blade thickness: 50 μm Dicing size: 5 mm x 5 mm Cut mode: Down cut After dicing, a foreign substance on the wafer (chip) is magnified (1)
The number of foreign matters (dicing scraps) was counted by observing at a magnification of 00. Table 1 shows the results.

[0042]

[Comparative Example] The same procedure as in Example was repeated except that the ethylene / methyl methacrylate copolymer film was replaced with a polyethylene film, an ethylene / ethyl acrylate copolymer film, or an ethylene vinyl acetate copolymer film. The results are shown in Table 1.

[0043]

[Table 1] EMMA: Ethylene / methyl methacrylate copolymer PE: Polyethylene EEA: Ethylene / ethyl acrylate copolymer EVA: Ethylene / vinyl acetate copolymer

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a pressure-sensitive adhesive sheet for wafer sticking according to the present invention.

FIG. 2 is a schematic sectional view of a pressure-sensitive adhesive sheet for wafer sticking according to the present invention.

FIG. 3 is a schematic cross-sectional view of a pressure-sensitive adhesive sheet for wafer sticking according to the present invention.

FIG. 4 is an explanatory diagram of a wafer dicing method according to the present invention.

FIG. 5 is an explanatory diagram of a wafer dicing method according to the present invention.

FIG. 6 is an explanatory diagram of a wafer dicing method according to the present invention.

FIG. 7 is an explanatory diagram of a wafer dicing method according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate film 2 ... Adhesive layer 3 ... Releasable sheet 4 ... Adhesive layer 5 ... Reinforcing layer 6 ... Push-up needle bar 7 ... Suction collet 8 ... Radiation source A ... Wafer B ... Radiation

Claims (4)

(57) [Claims] 1. A wafer sticking pressure-sensitive adhesive sheet comprising a base film and a pressure-sensitive adhesive layer, wherein the base film is an ethylene / methyl methacrylate copolymer film. 2. The ethylene / methyl methacrylate copolymer film contains 50 to 99% by weight of a structural unit derived from ethylene and 1 to 50% by weight of a structural unit derived from methylmethacrylic acid. The pressure-sensitive adhesive sheet for wafer sticking according to claim 1, wherein: 3. An ethylene / methyl methacrylate copolymer film is used as a substrate film when the wafer is attached to a wafer-attaching adhesive sheet consisting of a substrate film and an adhesive layer to dice the wafer. As a result, the wafer dicing method is characterized in that the amount of dicing debris generated during wafer dicing is reduced. 4. The ethylene / methyl methacrylate copolymer film contains 50 to 99% by weight of a structural unit derived from ethylene and 1 to 50% by weight of a structural unit derived from methylmethacrylic acid. The wafer dicing method according to claim 3, wherein.